I want to select just a class on its own called .date
For some reason, I cannot get this to work. If anyone knows what is wrong with my code, it would be much appreciated.
@$doc = new DOMDocument();
@$doc->loadHTML($html);
$xml = simplexml_import_dom($doc); // just to make xpath more simple
$images = $xml->xpath('//[@class="date"]');
foreach ($images as $img)
{
echo $img." ";
}
contains(@class, 'date')
I want to write the canonical answer to this question because the answer above has a problem.
Our problem
The CSS selector:
.foo
will select any element that has the class foo.
How do you do this in XPath?
Although XPath is more powerful than CSS, XPath doesn't have a native equivalent of a CSS class selector. However, there is a solution.
The right way to do it
The equivalent selector in XPath is:
//*[contains(concat(" ", normalize-space(@class), " "), " foo ")]
The function normalize-space strips leading and trailing whitespace (and also replaces sequences of whitespace characters by a single space).
(In a more general sense) this is also the equivalent of the CSS selector:
*[class~="foo"]
which will match any element whose class attribute value is a list of whitespace-separated values, one of which is exactly equal to foo.
A couple of obvious, but wrong ways to do it
The XPath selector:
//*[@class="foo"]
doesn't work! because it won't match an element that has more than one class, for example
<div class="foo bar">
It also won't match if there is any extra whitespace around the class name:
<div class=" foo ">
The 'improved' XPath selector
//*[contains(@class, "foo")]
doesn't work either! because it wrongly matches elements with the class foobar, for example
<div class="foobar">
Credit goes to this fella, who was the earliest published solution to this problem that I found on the web: http://dubinko.info/blog/2007/10/01/simple-parsing-of-space-seprated-attributes-in-xpathxslt/
//[@class="date"] is not a valid xpath.
Try //*[@class="date"], or if you know it is an image, //img[@class="date"]
XPath 3.1 introduces a function contains-token and thus finally solves this ‘officially’. It is designed to support classes.
Example:
//*[contains-token(@class, "foo")]
This function makes sure that white space (not only (U+0020)) is handled correctly, works in case of class name repetition, and generally covers the edge cases.
Note: As of today (2016-12-13) XPath 3.1 has status of Candidate Recommendation.
In XPath 2.0 you can:
//*[count(index-of(tokenize(@class, '\s+' ), 'foo')) = 1]
as stated by Christian Weiske in: https://cweiske.de/tagebuch/XPath%3A%20Select%20element%20by%20class.htm
HTML allows case-insensitive element and attribute names and then class is a space separated list of class-names. Here we go for a img tag and the class named date:
//*['IMG' = translate(name(.), 'abcdefghijklmnopqrstuvwxyz', 'ABCDEFGHIJKLMNOPQRSTUVWXYZ')]/@*['CLASS' = translate(name(.), 'abcdefghijklmnopqrstuvwxyz', 'ABCDEFGHIJKLMNOPQRSTUVWXYZ') and contains(concat(' ', normalize-space(.), ' '), concat(' ', 'date', ' '))]
See as well: CSS Selector to XPath conversion
BEWARE OF MINUS SIGNS IN TEMPLATE !!! If you are querying for "my-ownclass" in DOM:
<ul class="my-ownclass"><li>...</li></ul>
<ul class="someother"><li>...</li></ul>
<ul><li>...</li></ul>
$finder = new DomXPath($dom);
$nodes = $finder->query(".//ul[contains(@class, 'my-ownclass')]"); // This will NOT behave as expected! This will strangely match all the <ul> elements in DOM.
$nodes = $finder->query(".//ul[contains(@class, 'ownclass')]"); // This will match the element.
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<div class="foo\tbar">? I mean, class names separated by a tab.//*[contains(concat(" ", normalize-space(@class), " "), " foo ")]?